Micro-electro-mechanical device and method of manufacturing the same

ABSTRACT

The present invention improves mechanical strength of a micro-electro-mechanical device (MEMS) having a movable portion to improve reliability. In a micro-electro-mechanical device (MEMS) having a movable portion, a portion which has been a hollow portion in the case of a conventional structure is filled with a filler material. As the filler material, a block copolymer that is highly flexible is used, for example. By filling the hollow portion, mechanical strength improves. Besides, warpage of an upper portion of a structure body in the manufacture process is prevented, whereby yield improves. A micro-electro-mechanical device thus manufactured is highly reliable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.12/265,177, filed Nov. 5, 2008, now allowed, which claims the benefit ofa foreign priority application filed in Japan as Ser. No. 2007-289224 onNov. 7, 2007, both of which are incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a micro-electro-mechanical deviceincluding a microstructure body provided with a movable portion.Further, the present invention relates to a method of manufacturing themicro-electro-mechanical device.

2. Description of the Related Art

In recent years, research on micro-electro-mechanical systems (MEMS) hasbeen actively developed. “MEMS” is an acronym of amicro-electro-mechanical system and simply called a “micromachine” insome cases. The term “micromachine” generally refers to a micro devicein which “a movable microstructure body having a stereoscopic structure”and “an electronic circuit having a semiconductor element” that aremanufactured using a semiconductor microfabrication technology areintegrated. A microstructure body described above is different from thesemiconductor element and generally has a movable portion.

A microstructure body described above includes a structure layer and ahollow portion, and a structure layer includes a movable portion.Because of operation of a movable portion of a structure layer,mechanical strength is needed for a microstructure body described above.In Reference 1: Japanese Published Patent Application No. 2007-1004, asan example of a microstructure body having high mechanical strength, amicromachine that has a layer containing polycrystalline siliconcrystallized by heat crystallization using metal or lasercrystallization and a space below or above this layer is disclosed.

SUMMARY OF THE INVENTION

A conventional microstructure body includes a hollow portion in order toensure an operation region of a movable portion. For forming a hollowportion, a sacrificial layer is first formed in a portion which is to bea hollow portion, after a structure layer or the like is formed, thissacrificial layer is removed by etching or the like. For example, in thecase of a microstructure body in which a movable portion of a structurelayer operates in a direction perpendicular to a substrate surface, alower portion of the microstructure body is formed, a sacrificial layeris formed over this lower portion of the microstructure body, an upperportion of the microstructure body is formed over this sacrificiallayer, and the sacrificial layer is removed by etching or the like. Inthis manner, a microstructure body including a hollow portion is formed.

However, when a hollow portion is formed using a sacrificial layer, asdescribed above, there is a problem in that a microstructure body iseasily damaged or broken due to strong contact or the like between anupper electrode and a lower electrode of the microstructure body duringa manufacturing process. Further, there is a problem in that normaloperation becomes impossible by sticking between an upper electrode anda lower electrode. Here, the term “sticking” means a phenomenon inwhich, due to operation of a movable portion of a microstructure, anupper electrode and a lower electrode are in strong contact with eachother such that the upper electrode and the lower electrode can neverseparate from each other.

Furthermore, when a hollow portion is formed using a sacrificial layer,there is a problem in that the sacrificial layer is not completelyetched whereby etching residue is generated.

Alternatively, because of operation of an upper portion of amanufactured microstructure body, the microstructure body is potentiallydamaged or broken. This is particularly remarkable when the height of ahollow portion is high or when the toughness of a structure layer is notenough.

Furthermore, when a hollow portion is provided, there is a problem inthat a structure body including the hollow portion is deformed by, forexample, being wrapped and accordingly a desired structure cannot beobtained.

The present invention provides a microstructure body having a structurein which a pair of electrodes facing each other is isolated from eachother by a space, a movable structure body is provided with at least oneof the electrodes, and an insulating material fills this space. As thisinsulating material, a material having pores such that a filler materiallayer made up of this insulating material can be deformed when a movableportion operates is used. It is preferable to use a material which cansoften or harden by certain treatment (e.g., heat treatment or chemicalsolution treatment) after formation.

One aspect of the present invention is a micro-electro-mechanical deviceincluding a microstructure body. The microstructure body includes alower electrode layer over an insulating surface; a filler materiallayer over the lower electrode layer; an upper electrode layer facingthe lower electrode layer, over the filler material layer; and astructure layer over the upper electrode layer. The structure layer hasa structure capable of moving in a direction toward the lower electrodelayer or in a direction opposite to the direction toward the lowerelectrode layer. The filler material layer includes an insulatingmaterial provided with at least one pore reaching a surface of thefiller material layer. Porosity is greater than or equal toapproximately 20% and less than or equal to 80%.

In the above structure of the present invention, the porosity of thefiller material layer is greater than or equal to approximately 20% andless than or equal to 80%. This is because the filler material layeritself is difficult to form or because pores included in the fillermaterial layer are difficult to form when the porosity of the fillermaterial layer is above or below this range.

In the above structure of the present invention, the filler materiallayer can be formed of a block copolymer. When the filler material layerincludes a block copolymer, by setting the porosity to greater than orequal to 20% and less than or equal to 80%, the filler material layeritself or pores included in the filler material layer can be formed.More preferably, the porosity is set to greater than or equal to 20% andless than or equal to 60%. Further preferably, the porosity is set togreater than or equal to 20% and less than or equal to 35%.

One aspect of the present invention is a method of manufacturing amicro-electro-mechanical device, including the steps of forming a lowerelectrode layer over an insulating surface, forming a first fillermaterial layer so as to cover the lower electrode layer, forming anupper electrode layer over the first filler material layer, forming astructure layer over the upper electrode layer, preferably performingheat treatment, and forming a porous second filler material layer byremoving by etching any of the materials included in the first fillermaterial layer.

One aspect of the present invention is a method of manufacturing amicro-electro-mechanical device, including the steps of forming a lowerelectrode layer over an insulating surface, forming a film including ablock copolymer so as to cover an entire surface of the lower electrodelayer, selectively forming a metal mask over the film formed of theblock copolymer, forming a first filler material layer by etching thefilm formed of the block copolymer using the metal mask, forming anupper electrode layer over the first filler material layer, forming astructure layer over the upper electrode layer, preferably performingheat treatment, and forming a porous second filler material layer byremoving by etching any of the materials included in the first fillermaterial layer.

In any of the above structures of the present invention, the porosity ofthe second filler material layer is preferably greater than or equal to20% and less than or equal to 80%. More preferably, the porosity is setto greater than or equal to 20% and less than or equal to 60%. Furtherpreferably, the porosity is set to greater than or equal to 20% and lessthan or equal to 35%.

By applying the present invention, damage or breakage of amicrostructure body due to operation of an upper portion of themanufactured microstructure body can be prevented. Accordingly, evenwhen the height of a hollow portion is high or when the toughness of astructure layer is not enough, a microstructure body can bemanufactured.

Sticking does not occur in the microstructure body to which the presentinvention is applied, and thus a microstructure body capable ofrepetitive operation can be manufactured.

Further, a sacrificial layer is not needed to be formed in amanufacturing process, and thus a microstructure body can bemanufactured with high yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate an example of a microstructure body accordingto one aspect of the present invention.

FIGS. 2A and 2B illustrate an example of a conventional microstructurebody.

FIGS. 3A to 3G illustrate an example of a method of manufacturing amicrostructure body according to one aspect of the present invention.

FIGS. 4A to 4G each illustrate a phase of a block copolymer applicableto the present invention.

FIG. 5 is a block diagram illustrating an example of amicro-electro-mechanical device including a microstructure bodyaccording to one aspect of the present invention.

FIGS. 6A-1 to 6C-2 illustrate an example of a method of manufacturing amicro-electro-mechanical device including a microstructure bodyaccording to one aspect of the present invention.

FIGS. 7A-1 to 7B-2 illustrate an example of a method of manufacturing amicro-electro-mechanical device including a microstructure bodyaccording to one aspect of the present invention.

FIGS. 8A-1 to 8B illustrate examples of methods of manufacturingmicro-electro-mechanical devices including microstructure bodiesaccording to aspects of the present invention.

FIGS. 9A-1 to 9B-2 illustrate examples of methods of manufacturingmicro-electro-mechanical devices including microstructure bodiesaccording to aspects of the present invention.

FIGS. 10A and 10B illustrate examples of a micro-electro-mechanicaldevice including a microstructure body according to one aspect of thepresent invention.

FIGS. 11A and 11B each illustrate an example of a microstructure bodyaccording to one aspect of the present invention.

FIGS. 12A and 12B illustrate a strain gauge to which a microstructurebody according to one aspect of the present invention is applied.

FIG. 13 illustrates a strain gauge to which a microstructure bodyaccording to one aspect of the present invention is applied.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the present invention are describedwith reference to the accompanying drawings. However, the presentinvention is not limited to description below. This is because it iseasily understood by those skilled in the art that a variety of changesmay be made in modes and details without departing from the spirit andthe scope of the present invention. Therefore, the present inventionshould not be construed as being limited to description of theembodiment modes given below.

(Embodiment Mode 1)

A microstructure body and a method of manufacturing themicro-electro-mechanical device of the present invention are describedwith reference to drawings.

FIGS. 1A and 1B are, respectively, a cross-sectional view and a top viewof an example of a microstructure body of the present invention. In themicrostructure body of FIGS. 1A and 1B, a lower electrode layer 101 isprovided over a substrate 100, and a filler material layer 102 isprovided over the lower electrode layer 101. An upper electrode layer103 is provided over the filler material layer 102, and a structurelayer 104 is provided over the upper electrode layer 103. The distancebetween the lower electrode layer 101 and the upper electrode layer 103is denoted by d(m).

The lower electrode layer 101 and the upper electrode layer 103 areisolated from each other by the filler material layer 102 to form acapacitor. Here, when it is assumed that the area of the lower electrodelayer 101 is equal to the area of the upper electrode layer 103 anddenoted by S(m²), the capacitance of this capacitor is denoted by C(F),and the dielectric constant of the capacitor is denoted by ∈(F/m), anequation (1) below is obtained.

$\begin{matrix}{C = \frac{ɛ\; S}{d}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Here, when the structure layer 104 is pressed down, the distance dbetween the lower electrode layer 101 and the upper electrode layer 103is changed, whereby the capacitance is changed. The amount of change ΔCin capacitance at this time is represented by an equation (2) belowusing C₀ denoting the capacitance before the structure layer 104 ispressed down and C₁ denoting the capacitance after the structure layer104 is pressed down.ΔC=C ₁ −C ₀  [Equation 2]

That is, when d₀ denotes the distance before the structure layer 104 ispressed down and d₁ denotes the distance after the structure layer 104is pressed down, ΔC is represented by an equation (3) below.

$\begin{matrix}{{\Delta\; C} = {{\frac{ɛ\; S}{d_{1}} - \frac{ɛ\; S}{d_{0}}} = {\frac{ɛ\; S}{d_{0}d_{1}}\left( {d_{0} - d_{1}} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Thus, by finding out ΔC, the amount of change in the distance d betweenthe lower electrode layer 101 and the upper electrode layer 103 isobtained.

Note that FIGS. 2A and 2B illustrate an example of a conventionalmicrostructure body. A portion of the filler material layer 102 in themicrostructure body of FIGS. 1A and 1B corresponds to a hollow portion110 in the microstructure body of FIGS. 2A and 2B.

Next, an example of a method of manufacturing the microstructure bodyshown in FIGS. 1A and 1B is described with reference to drawings. First,the lower electrode layer 101 is selectively formed over the substrate100 (see FIG. 3A).

There is no particular limitation on the substrate 100. Although, forexample, a semiconductor substrate, a glass substrate, a quartzsubstrate, a plastic substrate, a stainless steel substrate, or the likecan be used, an insulating substrate is preferably used. When asemiconductor substrate or a stainless steel substrate is used, aninsulating film is preferably formed over this substrate to form aninsulating surface.

For example, the lower electrode layer 101 can be formed as follows. Aconductive film is formed over the substrate 100, a resist mask isformed over this conductive film by a photolithography method, and adesired portion of the conductive film is removed using this resist maskby etching or the like, so that the lower electrode layer 101 can beselectively formed. There is no particular limitation on a material forforming the lower electrode layer 101, and a material havingconductivity may be used. As the material having conductivity, anelement selected from tantalum, tungsten, titanium, molybdenum,aluminum, and copper; or an alloy material or a compound materialcontaining any of these elements as the main component may be used.Alternatively, silicon to which an impurity element having oneconductivity type is added or a transparent conductive film of indiumtin oxide (ITO) or the like may be used. Note that there is noparticular limitation on a formation method as well, and a sputteringmethod, a CVD method, a droplet discharging method, or the like can beused. By using a droplet discharging method, a desired pattern can beformed without etching, whereby the number of steps is reduced. Notethat the lower electrode layer 101 may be a single layer or a stack of aplurality of layers.

Next, the filler material layer 102 is formed over the lower electrodelayer 101. The filler material layer is formed of an organic materialand thus difficult to pattern by etching using a resist mask. Therefore,the case where a metal film is used as a mask is described below.

First, an organic film 120 is formed to cover the lower electrode layer101; a metal film 121 is formed over the organic film 120; and a resistmask 122 is selectively formed over the metal film 121 (see FIG. 3B).The organic film 120 is formed using a material for forming the fillermaterial layer 102 described later. For a formation method, a spincoating method or the like may be used, for example.

Next, the metal film 121 is etched using the resist mask 122, therebyforming a metal mask 123 (see FIG. 3C). For etching the metal film, acondition may be set depending on a material for the metal film. Whenthe material for the metal film 121 is, for example, tungsten, dryetching in a chlorine gas atmosphere can be used. It is preferable toemploy a condition providing high etching selectivity between the resistmask 122 and the organic film 120 (that is, a condition providing a highetching rate for the metal film 121 and a low etching rate for theorganic film 120 and the resist mask 122). Thereafter, the resist mask122 is removed.

Next, the organic film 120 is etched using the metal mask 123, therebyforming the filler material layer 102 (see FIG. 3D). For etching theorganic film 120, dry etching may be performed using, for example, anoxygen gas. Thereafter, the metal mask 123 is removed. Note that themetal mask 123 is not necessarily removed and may be used as the upperelectrode of the microstructure body.

Note that the example in which etching using a metal mask is employedfor forming the filler material layer 102 is described above, thepresent invention is not necessarily limited to this example. Forexample, a pattern can also be formed by mixing a photosensitivematerial into the organic film 120 and performing light exposure.

As described above, the filler material layer 102 can be selectivelyformed over the lower electrode layer 101 (see FIG. 3E). The fillermaterial layer 102 may be deformed depending on the movement of themicrostructure body and therefore is formed of a material film that canwithstand this deformation. After this material film is formed, adesired portion of the material film is removed by etching or the likein a similar manner to that of the lower electrode layer 101, so thatthe filler material layer 102 can be selectively formed. Alternatively,the filler material layer 102 may be selectively formed by a dropletdischarging method.

As the material for the filler material layer 102 of the presentinvention, a porous material which can be deformed is used. It ispreferable to use a material which can soften or harden by certaintreatment (e.g., heat treatment or chemical solution treatment) afterthe formation. As such a material, a block copolymer or a graftcopolymer that forms a microphase separation structure is given, forexample.

The term “block copolymer” means a straight chain copolymer including aplurality of homopolymer chains as blocks linked together. For example,a diblock copolymer is given. Further, a block copolymer typified by atriblock copolymer, which includes more than three kinds of polymerchains linked together, may be used.

The term “graft copolymer” means a copolymer having a structure in whichother polymer chains as side chains are linked to the main chain of thepolymer. The polymer chains linked as side chains may be of differentkinds.

Note that for the material forming the filler material layer 102, ablock copolymer is preferably used. This is because with a blockcopolymer, a polymer with a narrow molecular weight distribution can bereadily obtained and a composition ratio can be relatively easilycontrolled. By controlling the composition ratio of the material for thefiller material layer 102, the volume occupied by a pore per unit volumeof the filler material layer 102 can be controlled. Thus, the amount ofdeformation of the filler material layer 102 for unit load can bevaried. Hereinafter, a block copolymer which can be applied to thepresent invention is described.

It is known that a block copolymer spontaneously forms a nanometer-scalemicrophase separation structure. For example, an AB block copolymer ismicrophase-separated to form a periodic structure such as a sphericalstructure, a cylinder structure, a gyroid structure, or a lamellarstructure depending on the composition ratio of high molecule includedin the block copolymer. Note that when the rate of one of the componentsis less than or equal to approximately 20%, a spherical structure isformed (see FIG. 4A or 4E); when the rate is greater than or equal toapproximately 20% and less than or equal to approximately 35%, acylinder structure is formed (see FIG. 4B or 4D); when the rate isgreater than or equal to approximately 35% and less than or equal toapproximately 40%, a gyroid structure is formed (see FIG. 4F or 4G), andwhen the rate is greater than or equal to approximately 40%, a lamellarstructure is formed (see FIG. 4C). Note that a chemical solution doesnot easily reach a surface of the filler material layer in wet etchingand thus one of the components which should be removed is difficult toremove in the case of a spherical structure and therefore a cylinderstructure, a gyroid structure, or a lamellar structure is preferablyemployed.

For production of a block copolymer, a living polymerization method canbe used, for example. The living polymerization method refers to amethod by which polymerization of one kind of monomer is initiated by apolymerization initiator that generates anions or cations and anothermonomer is sequentially added for synthesis, so that a block copolymeris produced. The production method is described below.

First, components of a block copolymer are dissolved in a solvent. Thissolvent is preferably a good solvent for all the plural kinds ofpolymers included in the block copolymer. Here, the term “good solvent”means a solvent that can produce a homogeneous solution of the polymersincluded in the block copolymer. Because two kinds of polymers are usedhere, a homogeneous solution of the two kinds of polymers may beproduced. For example, a toluene solution of about 5% by weight of theblock copolymer is applied to a region where the filler material layer102 is to be formed by a spin coating method or the like. Note thatalthough a solution is applied to the entire surface of a substrate in aspin coating method, a solution is applied to only a desired region byusing a droplet discharging method, for example, whereby a later processis simplified and further utilization efficiency of a material isimproved; thus, use of such droplet discharging method or the like ispreferable.

Next, heat treatment is performed on the substrate to which the abovesolution is applied, thereby inducing microphase separation. Atemperature during the heat treatment is set to greater than or equal tothe glass transition point of the components included in the blockcopolymer and less than or equal to the phase transition temperaturethereof.

Note that there is a variety of kinds of block copolymers, typically, astyrene-butadiene AB block copolymer and a styrene-isoprene AB blockcopolymer. Besides, there is a block copolymer made up of differentmaterials, such as polymethylmethacrylate (PMMA); a block copolymerobtained by attaching a modifying group to a terminal group of astyrene-isoprene block copolymer; and the like. Examples of a highmolecular segment of the block copolymer include hydrophobic aromatichydrocarbon chains such as polystyrene and polyfluorene, hydrophobicaliphatic unsaturation hydrocarbon chains such as polybutadiene andpolyisoprene, hydrophilic aliphatic hydrocarbon chains such as polyvinylalcohol and polyethylene glycol, hydrophilic aromatic hydrocarbon chainssuch as polyvinyl pyridine and polystyrene sulfonic acid, hydrophobicsiloxanes such as poly dimethylsiloxane, metal complexes such as polyferrocene, and the like. Further, the block copolymer is linear,branched, or cyclic by covalent bond of two or more kinds of these highmolecular segments at one or more bonding points.

The above material may further contain a solvent. Examples of thesolvent include aliphatic hydrocarbons such as hexane, heptane, andoctane; halogenated hydrocarbons such as carbon tetrachloride,chloroform, and dichloromethane; aromatic hydrocarbons such as benzene,toluene, and xylene; ketones such as acetone and methyl ethyl ketone;ethers such as dimethyl ether and diethyl ether; alcohols such asmethanol and ethanol; water; and the like. The solvent can be selectedamong these solvents depending on properties or conditions of a materialwhich is to be formed.

In this embodiment mode, the filler material layer can be formed andselective removal of one of the components of a block copolymer byetching is achieved. Further, an ABA block copolymer or a BAB blockcopolymer can also have any of a variety of structures such as aspherical structure and a lamellar structure according to thecomposition of the block copolymer. Note that in the present invention,it is preferable to employ a cylinder structure, a gyroid structure, ora lamellar structure, as described above.

Note that in this embodiment mode, a material which can be applied tothe filler material layer 102 is not limited to the materials describedabove and may be a material made of plural kinds of substances, in whichone kind of substance can be removed by etching or the like in a laterstep. Further, although the substance removed by etching or the like isnot necessarily one kind of substance, it is necessary at the very leastthat at least one kind of substance in the filler material layer 102 benot removed by etching or the like to remain. Further, heat resistanceand chemical resistance are needed such that the material can withstanda process after the formation. Here, the substance remaining in thefiller material layer 102 without being removed is preferably capable ofelastic deformation.

Next, the upper electrode layer 103 is formed over the filler materiallayer 102 (see FIG. 3F). The upper electrode (second electrode) isformed to face the lower electrode (first electrode). The upperelectrode layer 103 may be formed using a material and a method whichare similar to those of the lower electrode layer 101. That is, aconductive film may be formed over the entire surface, and then adesired portion of the conductive film may be removed by etching or thelike.

Next, the structure layer 104 is selectively formed over the upperelectrode layer 103 so as to cover the filler material layer 102 (seeFIG. 3G). For forming the structure layer 104, in a similar manner tothat of the first electrode layer and the like, a material film may beformed over the entire surface, and then a desired portion of thismaterial film may be removed by etching.

A material for the structure layer 104 is not limited to a particularmaterial as long as the material has some toughness. For example, asilicon oxynitride film, a silicon nitride film, or the like can beused. Here, although a silicon oxynitride film or a silicon nitride filmmay be formed by a CVD method or the like, there is no particularlimitation on a formation method as well.

Note that an opening portion may be formed in the structure layer 104such that one of the materials contained in the filler material layer102 is removed by etching or the like. Furthermore, an opening portionmay also be formed in the upper electrode layer 103; however, theopening portion is not formed in the case where etching is performedbefore the upper electrode layer 103 is formed. Note that the number ofthe opening portion is not necessarily limited to one and that a minuteopening portion is preferably formed in any portion of the fillermaterial layer 102. Hereinafter, the case where a block copolymer isused for the filler material layer 102 is described.

In order to remove one of the components of the block copolymer, dryetching or wet etching can be used. For example, a reactive ion etching(RIE) method in an oxygen gas atmosphere can be used. It is preferableto adopt a condition in which etching rates of a component which shouldbe removed and a component to remain in the block copolymer are greatlydifferent from each other. In general, the higher the content of carbonmolecules per unit molecule contained in a polymer molecular chain is,the higher etching tolerance is; the lower the content of oxygenmolecules per segment is, the lower etching tolerance is. For example,because polystyrene (PS) contains an aromatic ring, the content ofcarbon molecules in a block copolymer ofpolystyrene-polymethylmethacrylate (PS-PMMA) is high; thus, the etchingtolerance of the block copolymer is high. The etching tolerance ofpolyacrylamide (PAAM) is low since the content of oxygen molecules ishigh. In the case of using an RIE method, the etching rate of one ofthese two kinds of components is generally four times that of the other.

Note that a gas used for the etching is not limited to an oxygen gas andmay be CF₄, H₂, C₂F₆, CHF₃, CH₂F₂, CF₃Br, NF₃, Cl₂, CCl₄, HBr, SF₆ orthe like.

Note that etching rate is determined per monomer unit of a blockcopolymer. It is known that when N denotes the total number of atoms permonomer unit, Nc denotes the number of carbon atoms per monomer unit,and No denotes the number of oxygen atoms per monomer unit, etching rateis proportional to N/(Nc−No).

However, in the above dry etching method, although there is no problemin the case of a cylinder structure or the like, many portions couldfail to be etched in the case of a spherical structure. Thus, in thecase of a spherical structure, a wet etching method is preferably used.By a wet etching method, one of the components can be etched accordingto the material for a formed block copolymer and the other of thecomponents may be etched under a condition of high etching tolerance.However, in consideration of the above circumstances, it is morepreferable to employ a cylinder structure, a gyroid structure, or alamellar structure.

Further, a method of removing the component which should be removed isnot necessarily limited to etching. If possible, the component whichshould be removed may be removed by vaporization, sublimation, or thelike by heat treatment or the like.

As described above, the microstructure body of the present invention canbe formed. In the microstructure body of the present invention, unlike aconventional microstructure body, the hollow portion is filled with amaterial that can be deformed. Accordingly, a microstructure body havingmechanical strength higher than a conventional microstructure bodyincluding a hollow portion can be manufactured. The improvement inmechanical strength makes it possible to prevent generation of a defectduring a manufacturing process or operation to improve yield andreliability.

Further, since the microstructure body of the present invention has nohollow portion, a sacrificial layer is not needed to be formed. Thus, astep of forming a sacrificial layer and a step of removing it are notneeded, whereby the number of manufacturing steps can be reduced.Further, in manufacture of a conventional microstructure body, when asacrificial layer is not sufficiently removed by etching, yield may bereduced by a remaining portion of the sacrificial layer. By applying thepresent invention, such a reduction in yield due to a remaining portionof a sacrificial layer can be prevented, whereby yield improves.

Further, when a strain gauge is formed of the upper electrode layer 103and the structure layer 104 in the microstructure body, the lowerelectrode layer 101 is not necessarily formed. Furthermore, the presentinvention can be applied not only to a sensor but also to an actuator.

Alternatively, by applying bimetal to the structure layer 104, anactuator that drives by a bimetal effect can be manufactured.

By using such a microstructure body, a dynamic sensor can bemanufactured. With this dynamic sensor, a pressure sensor can bemanufactured, for example. Further, with the above actuator, a displaydevice or the like using an interference method can be manufactured.

Further, although the case is described in the above description inwhich the side face of the filler material layer does not have a taperedshape, the present invention is not limited to this case, and the sideface of the filler material layer may have a tapered shape (see FIG.11A). In the microstructure body shown in FIG. 11A, a lower electrodelayer 131 is provided over the substrate 100, and a filler materiallayer 132 is provided to cover the lower electrode layer 131. An upperelectrode layer 133 is provided over the filler material layer 132, anda structure layer 134 is provided over the upper electrode layer 133. Aside face of the filler material layer 132 is processed to have atapered shape. With the side face of the filler material layer 132having a tapered shape, the structure layer and the like formed overthis filler material layer 132 can be formed in an excellent manner.Accordingly, disconnection of a wiring electrically connected to thelower electrode layer 131 and the upper electrode layer 133 of themicrostructure body can be prevented, whereby yield in the manufacturingprocess improves.

Furthermore, the filler material layer of the present invention can alsobe formed by a droplet discharging method (see FIG. 11B). In themicrostructure body shown in FIG. 11B, a lower electrode layer 136 isprovided over the substrate 100, and a filler material layer 137 isprovided to cover the lower electrode layer 136. An upper electrodelayer 138 is provided over the filler material layer 137, and astructure layer 139 is provided over the upper electrode layer 138. Thefiller material layer 137 formed by a droplet discharging method isformed to have a curved shape. That is, a surface of the filler materiallayer may be formed so as to be curved.

As described above, the present invention is not limited to one mode andcan be applied to microstructure bodies having a variety of structures.By providing a filler material layer in a space corresponding to ahollow portion in a conventional microstructure body, a manufacturemicrostructure body including a movable portion with high mechanicalstrength and high reliability can be manufactured with high yield.

Note that only the simplest example is described in this embodiment modeand that a variety of modes can be implemented depending on a functionof a microstructure body.

(Embodiment Mode 2)

In this embodiment mode, an example of a structure of a semiconductordevice of the present invention and a manufacturing method of thesemiconductor device are described with reference to drawings.

A semiconductor device of the present invention belongs to a field of amicromachine and generally ranges in size from micrometers tomillimeters. Further, the semiconductor device may be in meters for easeof assembling when manufactured to be incorporated as a component of acertain mechanical device.

FIG. 5 is a block diagram of an example of the semiconductor device ofthe present invention. The semiconductor device 231 of the presentinvention includes an electric circuit portion 232 and a structureportion 233. The electric circuit portion 232 is formed using asemiconductor element and includes a control circuit 234 for controllingthe structure portion 233 and an interface 235 for communicating with anexternal control device 230. Further, the structure portion 233 includesa sensor 236, an actuator 237, a switch, and the like formed using amicrostructure body. The structure portion 233 may include one of asensor, an actuator, and a switch.

Further, the electric circuit portion 232 may include a centralprocessing unit for processing data obtained by the structure bodyportion 233, a memory for storing processed data, and the like.

The external control device 230 performs operation, such as transmissionof signals for controlling the semiconductor device 231, reception ofdata obtained by the semiconductor device 231, or supply of drivingpower to the semiconductor device 231.

Note that the present invention is not limited only to the abovestructure example. That is, the semiconductor device of the presentinvention may include an electric circuit for controlling amicrostructure body and the microstructure body controlled by theelectric circuit, and other structures of the semiconductor device arenot limited to those in FIG. 5.

Next, in order to manufacture the above-described semiconductor deviceof the present invention, a method of forming a microstructure body anda semiconductor element over one substrate is described with referenceto FIGS. 6A-1 to 6C-2, FIGS. 7A-1 to 7B-2, and FIGS. 8A-1 to 8B. Eachdrawing is a top view or a cross-sectional view taken along a line O-Pin the top view.

The microstructure body of the present invention and the semiconductorelement can be formed over a substrate having one insulating surface(hereinafter referred to as an insulating substrate). Here, as theinsulating substrate, there are a glass substrate, a quartz substrate, aplastic substrate, and the like. Alternatively, a conductive substrateof metal or the like, or a semiconductor substrate of silicon or thelike, over which a layer having an insulating property is formed, may beused. By forming the microstructure body and the semiconductor elementover one plastic so substrate, a highly flexible and thin semiconductordevice can be manufactured. Further, by thinning a glass substrate bygrinding or the like, a thin semiconductor device can also bemanufactured.

In the semiconductor device of the present invention, the microstructurebody includes a filler material layer. The filler material layer ispreferably formed of a block copolymer, as described in EmbodimentMode 1. However, since a block copolymer does not have high heatresistance enough to withstand a manufacturing process of a thin filmtransistor in many cases, a manufacturing method in which a thin filmtransistor is formed first over a substrate and then the microstructurebody is formed is described in this embodiment mode.

First, a base film 202 is formed over an insulating substrate 201. Thebase film 202 is formed of a single layer or stacked layers of aninsulating film such as a silicon oxide based material film or a siliconnitride based material. Here, the case is described in which aninsulating film having a two-layer structure is formed as the base film202. Note that the base film 202 is not necessarily provided if notnecessary.

Note that the silicon oxide based material corresponds to silicon oxidecontaining oxygen and silicon as the main components, or siliconoxynitride which is silicon oxide containing nitrogen, in which thecontent of oxygen is higher than that of nitrogen. The silicon nitridebased material corresponds to silicon nitride containing nitrogen andsilicon as the main components, or silicon nitride oxide which issilicon nitride containing oxygen, in which the content of nitrogen ishigher than that of oxygen.

In this embodiment mode, the base film 202 has a two-layer structure. Asa first layer of the base film 202, for example, a silicon nitride basedmaterial film is formed to a thickness greater than or equal to 10 nmand less than or equal to 200 nm, preferably, greater than or equal to50 nm and less than or equal to 100 nm, using SiH₄, NH₃, N₂O, and H₂ asreaction gases by a plasma CVD method. Here, a silicon nitride oxidefilm with a thickness of 50 nm is formed. Next, as a second layer of thebase film 202, a silicon oxide based material film is formed over thefirst layer to a thickness greater than or equal to 100 nm and less thanor equal to 150 nm using SiH₄ and N₂O as reaction gases by a plasma CVDmethod. Here, a silicon oxynitride film with a thickness of 100 nm isformed.

Next, a semiconductor film is formed to be etched to have a certainshape, thereby fanning a semiconductor layer 204 (see FIGS. 6A-1 and6A-2). The semiconductor layer 204 can be formed of a materialcontaining silicon as the main component. As a material containingsilicon, there is a material made of silicon, a silicon germaniummaterial containing germanium at about 0.01 to 4.5 atomic %, and thelike.

For the semiconductor layer 204, a material having a crystallinestructure or an amorphous structure can be used. Here, an amorphoussemiconductor film is formed to be crystallized by heat treatment,thereby forming a crystalline semiconductor film. For the heattreatment, heating using a heating furnace, laser irradiation,irradiation with light emitted from a lamp instead of laser light(hereinafter referred to as lamp annealing), or a combination of any ofthe above can be used.

In the case of laser irradiation, continuous wave laser light (CW laserlight) or pulsed wave laser light (pulsed laser light) can be used. Asthe laser light, laser light emitted from one or a plurality of an Arlaser, a Kr laser, an excimer laser, a YAG laser, a Y₂O₃ laser, a YVO₄laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser, analexandrite laser, a Ti:sapphire laser, a copper vapor laser, and a goldvapor laser can be used. By irradiation with the fundamental waves ofsuch laser light or the second harmonic to the fourth harmonic laserlight of these fundamental waves, crystals with a large grain size canbe obtained. For example, a second harmonic (532 nm) or a third harmonic(355 nm) of an Nd:YVO₄ laser (a fundamental wave of 1064 nm) can beused. The energy density of the laser light in this case is set toapproximately greater than or equal to 0.01 MW/cm² and less than orequal to 100 MW/cm², preferably, greater than or equal to 0.1 MW/cm² andless than or equal to 10 MW/cm². Then, irradiation is conducted at ascanning rate of approximately greater than or equal to 10 cm/sec andless than or equal to 2000 cm/sec.

Note that the laser crystallization may be performed by irradiation withcontinuous wave laser light of a fundamental wave and continuous wavelaser light of a harmonic or irradiation with continuous wave laserlight of a fundamental wave and pulse-oscillation laser light of aharmonic.

Further, it is also possible to use pulsed laser light oscillated at arepetition rate that allows laser light of a next pulse to be deliveredbefore the semiconductor layer is solidified and after the semiconductorlayer is melted by previous laser light. By using laser light with sucha repetition rate, crystal grains that are grown continuously in thescan direction can be obtained. As a specific repetition rate of thelaser light, a repetition rate greater than or equal to 10 MHz is used.This is much higher than the normally used frequency band ranging fromseveral tens of Hz to several hundred Hz.

Alternatively, the heat treatment may be performed by other methodsinstead of the laser irradiation. For example, the heat treatment usinga heating furnace can be performed. In the case of using a heatingfurnace, the amorphous semiconductor film may be heated at a temperaturegreater than or equal to 400° C. and less than or equal to 550° C. forgreater than or equal to 2 hours and less than or equal to 20 hours. Atthis time, the temperature may be set at many steps in the range ofgreater than or equal to 400° C. and less than or equal to 550° C. so asto increase gradually. In the case of setting at many steps, with atemperature of about 400° C. at a first step, hydrogen etc. contained inthe amorphous semiconductor film is discharged. Accordingly, surfaceroughness of the film in the crystallization can be reduced, or removalof the film in the crystallization can be prevented. Furthermore, byusing a metal promoting crystallization, for example, nickel,crystallization at a relatively low temperature can be realized. As themetal promoting crystallization, instead of nickel, a metal such as Fe,Ru, Rh, Pd, Os, Ir, Pt, Cu, or Au can be used alternatively.

Further alternatively, both the heat treatment using a heating furnaceand the heat treatment using a laser may be used in combination for thecrystallization of the amorphous semiconductor film.

Note that the metal promoting crystallization may be a contaminant forthe semiconductor device and therefore is preferably removed or reducedafter the crystallization. In this case, after the crystallization bythe heat treatment using a heating furnace or using laser irradiation, alayer serving as a gettering sink is formed over the semiconductor layerand heated, so that the metal is moved into the gettering sink, wherebythe metal can be removed or reduced. As the gettering sink, apolycrystalline semiconductor film or a semiconductor film to which animpurity element is added can be used. For example, a polycrystallinesemiconductor film to which an inert element such as argon is added isformed over the semiconductor film, and can be used as the getteringsink. Addition of an inert element allows the polycrystallinesemiconductor film to have a distortion, thereby capturing the metaleffectively. Alternatively, the metal can be captured by forming asemiconductor film to which an element such as phosphorus is added.

Further, the semiconductor layer 204 is not limited to an amorphoussemiconductor film or a film obtained by crystallizing an amorphoussemiconductor film. For example, a single crystal semiconductor layerformed by bonding a semiconductor substrate provided with a damagedlayer formed by doping hydrogen ions or the like to the insulatingsubstrate 201 or the insulating substrate 201 provided with aninsulating film thereon and separating the semiconductor layer from thedamaged layer may be used. Note that here, an insulating film may alsobe provided on the bonding surface of the semiconductor substrate. Asemiconductor layer formed by such a process can exhibit excellentelectrical properties (e.g., high mobility), and accordingly ahigh-performance semiconductor device using a microstructure body of thepresent invention can be provided. For example, power consumption isreduced. Besides, an area covered by the electric circuit portion 232 inFIG. 5 can be reduced.

Next, a gate insulating film 206 is formed over the semiconductor layer204 (see FIGS. 6A-1 and 6A-2). In a similar manner to that of the basefilm 202, the gate insulating film 206 is formed using a silicon oxidebased material, a silicon nitride based material, or the like by aplasma CVD method, a sputtering method, or the like. In this embodimentmode, as the gate insulating film 206, a silicon oxynitride film havinga thickness of 110 nm is formed by a plasma CVD method. Naturally, thegate insulating film 206 is not limited to a silicon oxynitride film,and another insulating film containing silicon may be formed to have asingle layer or stacked layers.

Alternatively, the gate insulating film 206 can also be formed by ahigh-density plasma treatment. Here, the term “high-density plasmatreatment” means plasma treatment in which a plasma density is greaterthan or equal to 1×10¹¹ cm⁻³, preferably, greater than or equal to1×10¹¹ cm⁻³ and less than or equal to 9×10¹⁵ cm⁻³ and a high frequencywave such as a microwave (e.g., a frequency of 2.45 GHz) is used. Whenplasma is produced under such conditions, a low electron temperature isgreater than or equal to 0.2 eV and less than or equal to 2.0 eV. Thus,such high-density plasma at a low electron temperature has low kineticenergy of active species and makes it possible to form a film with lessplasma damage and fewer defects. In the insulating film formed by thehigh-density plasma treatment in this manner, the state of an interfacebetween this insulating film and the layer in contact with theinsulating film can be improved. Thus, when the gate insulating film 206is formed by high-density plasma treatment, the state of an interfacebetween the gate insulating film 206 and the semiconductor layer 204 canbe improved. Accordingly, electrical properties of the semiconductorelement can be improved.

Furthermore, the high-density plasma treatment can be used for formingnot only the gate insulating film 206 but also the base film 202 orother insulating layers.

Next, a conductive film serving as a gate electrode layer 207 includedin the semiconductor element is formed over the gate insulating film 206and is, for example, etched to have a desired shape (see FIGS. 6B-1 and6B-2). The gate electrode layer 207 can be formed using a metal havingconductivity, such as tungsten, a compound having conductivity, or thelike, by a sputtering method, a CVD method, or the like. Note that thegate electrode layer 207 may be formed of a stack of two or more kindsof conductive materials. Further, a side face may be etched to have atapered shape. Note that a tungsten film is formed to have a singlelayer, thereby forming the gate electrode layer.

A pattern for obtaining a desired shape is formed by forming a resistmask using a photolithography method and performing anisotropic dryetching. As an etching method, an inductively coupled plasma (ICP)etching method can be used, for example. Etching conditions (the amountof power applied to a coiled electrode, the amount of power applied toan electrode on the insulating substrate 201 side, a temperature of theelectrode on the insulating substrate 201 side, etc.) may be determinedin consideration of the thickness of a film which is to be etched. Notethat as an etching gas, a chlorine-based gas such as Cl₂, BCl₃, SiCl₄,or CCl₄; a fluorine-based gas such as CF₄, SF₆, or NF₃; or an O₂ gas canbe used.

Next, impurity elements are added to predetermined regions of thesemiconductor layer 204 to form a p-type impurity region 211 and ann-type impurity region 212 (see FIGS. 6C-1 and 6C-2). These impurityregions can be selectively formed by forming a resist mask by aphotolithography method and adding the impurity elements. As a methodfor adding the impurity elements, an ion doping method or an ionimplantation method can be employed. As an impurity element impartingn-type conductivity, phosphorus (P) or arsenic (As) can be typicallyused, and as an impurity element imparting p-type conductivity, boron(B) can be used.

Next, an insulating film made of a silicon nitride based material or asilicon oxide based material is formed by a plasma CVD method or thelike to be etched anisotropically in a perpendicular direction, therebyforming an insulating layer (hereinafter referred to as a sidewall 209)in contact with a side face of the gate electrode layer 207 (see FIGS.6C-1 and 6C-2).

Next, an impurity element is further added to the semiconductor layer204 having the n-type impurity region 212 to form a high-concentrationn-type impurity region 210 having an impurity concentration higher thanthat of the n-type impurity region 212 provided below the sidewall 209.

Further, when the gate electrode layer 207 is formed of a stack ofdifferent conductive materials and has a tapered-shaped side face, thesidewall 209 is not necessarily formed. This is because when the gateelectrode layer 207 has a tapered-shaped side face, the n-type impurityregion 212 and the high-concentration n-type impurity region 210 can beformed by adding an impurity element at a time.

Note that by forming the n-type impurity region 212 and thehigh-concentration n-type impurity region 210 as described above, thethin film transistor can have a lightly doped drain (LDD) structure. Byforming the thin film transistor having an LDD structure, a shortchannel effect can be prevented. The smaller the thin film transistoris, the more easily a short channel effect occurs; thus, the smaller thethin film transistor is, the more preferably an LDD structure isemployed. Note that only the n-type semiconductor element may have anLDD structure.

Next, after the impurity regions are formed, in order to activate theimpurity elements, heating or irradiation with infrared light or laserlight is performed. Further, at the same time as the activation, it ispossible to recover plasma damage of the gate insulating film 206 orplasma damage of the interface between the insulating film 206 and thesemiconductor layer 204. In particular, the impurity elements can beeffectively activated by using an excimer laser from the front or rearsurface of the substrate 201 in an atmosphere at room temperature to300° C. Further, a second harmonic of a YAG laser may be used for theactivation. A YAG laser is preferably used as a laser irradiation meansbecause maintenance of the YAG laser is not so frequently required.

Further, a passivation film made of an insulating material such assilicon oxynitride or silicon oxide may be formed so as to cover thesemiconductor layer 204 and the conductive layer which selves as thegate electrode layer 207. After the passivation film is formed, heating,infrared light irradiation, or laser light irradiation can be furtherperformed for hydrogenation. For example, a silicon oxynitride film isformed to a thickness of 100 nm by a plasma CVD method, and then heatingis performed using a clean oven at 300 to 550° C. for 1 to 12 hours,thereby hydrogenating the semiconductor layer 204. For example, heatingis performed using a clean oven in a nitrogen atmosphere at 410° C. forone hour. In this step, hydrogen is contained in the passivation film toterminate dangling bonds in the semiconductor layer 204, which is causedby the addition of the impurity element. Further, at the same time, theabove-described activation treatment of the impurity region can becarried out.

Through the above-described steps, an n-type semiconductor element 213and a p-type semiconductor element 214 which are thin film transistorsare formed (see FIGS. 6C-1 and 6C-2).

Subsequently, an interlayer insulating layer 215 is formed so as tocover the whole semiconductor element (see FIGS. 7A-1 and 7A-2). Theinterlayer insulating layer 215 can be formed of an inorganic or organicmaterial or the like having an insulating property. As the inorganicmaterial, silicon oxide, silicon nitride, or the like can be used. Asthe organic material, polyimide, acrylic, polyamide, polyimide-amide,benzocyclobutene, a siloxane resin, or polysilazane can be used. Notethat a siloxane resin corresponds to a resin containing a Si—O—Si bond.Siloxane has a skeleton structure with a silicon-oxygen bond. As asubstituent, an organic group (e.g., an alkyl group or an aromatichydrocarbon) or a fluoro group may be used. The organic group maycontain a fluoro group. Polysilazane is formed using a polymer materialhaving a silicon-nitrogen bond as a starting material.

Note that when the interlayer insulating layer 215 is formed of theinorganic material by a CVD method or the like, after being formed, theinterlayer insulating layer 215 is preferably planarized by a chemicalmechanical polishing (CMP) method or the like.

Next, the interlayer insulating layer 215 and the gate insulating film206 are sequentially etched to form a contact hole. As the etching, adry etching method or a wet etching method can be employed. In thisembodiment mode, the contact hole is formed by a dry etching method.

Next, a conductive layer 217 is formed over the interlayer insulatinglayer 215 and in the contact hole to be, for example, etched to have adesired shape, thereby forming a wiring for forming a source or drainelectrode layer and further the electric circuit (see FIGS. 7A-1 and7A-2). The conductive layer 217 can be formed using a film containing anelement such as aluminum, titanium, molybdenum, tungsten, or silicon, oran alloy film using any of these elements.

Further, when the conductive layer 217 is rectangular because of alayout limitation and thus has a pattern with a corner portion, thecorner portion is preferably, for example, etched to have a round shape.By the etching forming a round shape, generation of dust during amanufacturing process can be suppressed, whereby yield can be improved.This applies to the gate electrode layer, the semiconductor layer, andthe like.

Through the above-described steps, the thin film transistors, theinterlayer insulating layer 215 covering the thin film transistors, andthe conductive layer 217 serving as the wiring connected to the thinfilm transistors can be formed.

Next, the microstructure body is provided over the interlayer insulatinglayer 215. The process described in Embodiment Mode 1 may be applied toa method of manufacturing the microstructure body.

Note that here, the case is described in which the conductive layer 217serves as the source or drain electrode layer of the thin filmtransistor and the lower electrode of the microstructure body.Therefore, the lower electrode of the microstructure body has alreadybeen formed by the above process. However, the present invention is notlimited to this case, and the conductive layer 217 and the lowerelectrode of the microstructure body may be formed separately.

Next, a filler material layer 218 is formed to cover the lower electrodeformed of the conductive layer 217. The filler material layer 218 may beformed using a material and a method which are similar to those of thefiller material layer 102 in Embodiment Mode 1.

Next, a conductive layer 219 for forming an upper electrode is formedover the filler material layer 218 which is formed to have a desiredpattern, and a structure layer 220 is formed over the conductive layer219 which is formed to have a desired pattern. The conductive layer 219may be formed using a material and a method which are similar to thoseof the upper electrode layer 103 in Embodiment Mode 1, and the structurelayer 220 may be formed using a material and a method which are similarto those of the structure layer 104 in Embodiment Mode 1.

As described above, it is possible to form the microstructure body ofthe present invention and the transistor over one substrate (see FIGS.8A-1 and 8A-2).

Note that the conductive layer 217 may form the upper electrode, not thelower electrode of the microstructure body (see FIG. 8B).

Note that the case is described above in which the thin film transistoris used as the transistor, the present invention is not limited to thiscase and the transistor may be a field effect transistor (a FET).Further, a silicon-on-insulator (SOI) substrate may be used as thesubstrate (see FIGS. 10A and 10B). In FIG. 10A, the conductive layer 238serves as the source or drain electrode layer of the FET and the lowerelectrode of the microstructure body. In FIG. 10B, the conductive layer239 serves as the source or drain electrode layer of the FET and theupper electrode of the microstructure body.

Note that although the case where the transistor is formed and then themicrostructure body is formed over the interlayer insulating layerformed to cover this transistor is described in this embodiment mode,the present invention is not limited to this case. Each layer of themicrostructure body can also be formed while each layer of thetransistor is formed, as long as the filler material layer included inthe microstructure body is not damaged or deformed, for example, bytemperature during the manufacturing process of the transistor, the usedchemical solution, or the like. For example, the gate electrode of thetransistor and the lower electrode of the microstructure body can beformed by patterning one layer, and the source or drain electrode of thetransistor and the upper electrode of the microstructure body can beformed by patterning one layer. This can be realized by using an organictransistor, for example. The term “organic transistor” means atransistor to which an organic semiconductor such as pentacene isapplied. An example of a method of manufacturing an organic thin filmtransistor (hereinafter referred to as an organic TFT) is brieflydescribed below.

FIGS. 9A-1 and 9A-2 are respectively a top view and a cross-sectionalview of the case where a bottom contact organic TFT is used as thetransistor. In the case of the bottom contact organic TFT, after asource or drain electrode is formed, an organic semiconductor film isformed.

First, a base film 302 is formed over an insulating substrate 301, and agate electrode layer 307 is formed over the base film 302. The base film302 can be formed in a similar manner to that of the base film 202, andthe gate electrode layer 307 can be formed in a similar manner to thatof the gate electrode layer 207.

Note that as the insulating substrate 301, a substrate similar to theinsulating substrate 201 can be used. However, as the insulatingsubstrate 301, a substrate made of a synthetic resin such as plastictypified by polyethylene terephthalate (PET), polyethylene naphthalate(PEN), or polyether sulfone (PES), or acrylic may preferably be used.Such a substrate made of a synthetic resin is flexible and furtherlightweight.

Further, the gate electrode layer 307 may be formed by a sputteringmethod, a screen printing method, a roll coater method, a dropletdischarging method, a spin coating method, or an evaporation method. Foran electrode material, metal, a metal compound, a conducting polymer, orthe like may be used.

A droplet discharging method is a method capable of selectively forminga pattern, in which a droplet of a composition into which a material fora conductive film, an insulating film, or the like is mixed isselectively discharged (including jetting) to form the conductive film.A typical example of a droplet discharging method is an inkjet method.

When the conductive film is formed by a droplet discharging method, aconductor is mixed into a solvent. For the conductor which is to bemixed into the solvent, gold, silver, copper, platinum, palladium,tungsten, nickel, tantalum, bismuth, lead, indium, tin, zinc, titanium,or aluminum; an alloy containing any of the above; dispersiblenanoparticles of any of the above; or fine particles of silver halidecan be used.

When the conductive film is formed by a screen printing method or thelike, a conductive paste is used. As the conductive paste, a conductivecarbon paste, a conductive silver paste, a conductive copper paste, aconductive nickel paste, or the like can be used. After being formed tohave a predetermined pattern, the conductive paste may be dried,subjected to heat treatment at approximately 100 to 200° C. to beplanarized (also referred to as leveled), and hardened.

Note that with the gate electrode layer 307, not only the gate electrodeof the thin film transistor but also the lower electrode of themicrostructure body can be formed.

After the gate electrode layer 307 is formed, a gate insulating film 306is formed. The gate insulating film 306 may be formed using a materialand a method which are similar to those of the gate insulating film 206.Although a CVD method is used here, a sputtering method, spin coatingmethod, an evaporation method, or the like may be alternatively used.Alternatively, a siloxane resin, polysilazane, or the like may be usedin a similar manner to that of the interlayer insulating layer 215.Alternatively, as the gate insulating film, an insulating film formed byanodization of the gate electrode may be used.

Next, a filler material layer 318, an upper electrode layer 319, and astructure layer 320 of the microstructure body are formed. The fillermaterial layer 318 may be formed using a material and a method which aresimilar to those of the filler material layer 102 in Embodiment Mode 1.The upper electrode layer 319 may be formed using a material and amethod which are similar to those of the gate electrode layer 307. Thestructure layer 320 may be formed using a material and a method whichare similar to those of the structure layer 104 in Embodiment Mode 1.

Next, a source or drain electrode layer 316 of the thin film transistoris formed over the gate insulating film 306. The source or drainelectrode layer 316 can be formed using a material and a method whichare similar to those of the gate electrode layer 307. Note that an ohmiccontact between the source or drain electrode layer 316 and the organicsemiconductor film formed later is needed. Therefore, when an materialfor the organic semiconductor film has p-type conductivity, a materialhaving a work function higher than the ionization potential of thematerial for the organic semiconductor film is preferably used; when thematerial for the organic semiconductor film has n-type conductivity, amaterial having a work function lower than the ionization potential ofthe material for the organic semiconductor film is preferably used.Since pentacene that is a p-type material is used as the material forthe organic semiconductor film here, tungsten having a relatively highwork function is used as the material for the source or drain electrodelayer 316. However, there is no limitation to this example.

Next, the organic semiconductor film 304 is formed over the gateinsulating film 306 and the source or drain electrode layer 316. Asdescribed above, pentacene is used as the material for the organicsemiconductor film of this embodiment mode. However, the material forthe organic semiconductor film is not limited to this material and maybe an organic molecular crystal or an organic high molecular compound.As the organic molecular crystal, specifically, there are polycyclicaromatic compounds, conjugated double bond compounds, carotenes, andmacrocycle compounds; complexes of these compounds; phthalocyanine;charge transfer complexes (CT complexes); and the like. For example, itis possible to use anthracene, tetracene, pentacene, hexathiophene (6T),tetracyanoquinodimethane (TCNQ), atetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) complex,diphenylpicrylhydrazyl (DDPH), a pigment, a protein, aperylenetetracarboxylic acid derivative such as PTCDA, anaphthalenetetracarboxylic acid derivative such as NTCDA, or the like.Further, as the organic high molecular compound, specifically, there arepi-conjugated polymers, phthalocyanine metal complexes, iodinecomplexes, and the like. In particular, it is preferable to use api-conjugated polymer including a conjugated double bond, such aspolyacetylene, polyaniline, polypyrrole, polythienylene, a polythiophenederivative, poly(3-alkylthiophene), a polyparaphenylene derivative, or apolyparaphenylenevinylene derivative.

Further, a method by which a film having uniform thickness can be formedmay be used for forming the organic semiconductor film 304.Specifically, an evaporation method, a spin coating method, a barcoating method, a solution casting method, a dip coating method, or thelike may be used. Here, pentacene that is an organic semiconductormaterial is formed for the organic semiconductor film 304 over the gateinsulating film 306 and the source or drain electrode layer 316 by avacuum evaporation method that is a kind of evaporation method.Preferably, the organic semiconductor film 304 is selectively formed byformation through a mask, for example.

Note that as pretreatment for forming the organic semiconductor film,ultraviolet light irradiation treatment or plasma treatment may beperformed on a surface over which the organic semiconductor film is tobe formed. The plasma treatment or the like makes it possible to realizeremoval of organic substances on the surface over which the organicsemiconductor film is to be formed and an improvement in work function(to facilitate electron injection). Alternatively, a film for improvingadhesion to the surface over which the organic semiconductor film is tobe formed or improving an interface state, for example, a self-assembledmonolayer (SAM) film or an orientation film may be formed.

Then, after the organic semiconductor film is formed, the insulatingsubstrate 301 is subjected to heat treatment. The upper limit of thetemperature for the heat treatment is tower than the temperature atwhich the organic semiconductor film 304 is vaporized or decomposed.Heat treatment at a high temperature within this range improvescharacteristics of the organic TFT. Further, the temperature at thistime is preferably less than or equal to the melting point of theorganic semiconductor film.

Note that the heat treatment may be performed in an atmosphere butpreferably in an inert gas atmosphere of nitrogen, argon, or the like inconsideration of deterioration of the organic semiconductor film due tooxygen or water. Furthermore, the heat treatment is more preferablyperformed in a reduced pressure (e.g., 1.3×10⁻³ to 6.7×10⁴ Pa).

Note that the present invention is not limited to the above description,and that the microstructure body may be formed after the organic TFT isformed or the organic TFT may be formed after the microstructure body isformed.

As described above, the bottom contact organic TFT and themicrostructure body can be formed over one substrate (see FIGS. 9A-1 and9A-2).

Note that the organic TFT of the present invention is preferably coveredwith a protective film. Here, an insulating inorganic film is used asthe protective film. By covering the organic TFT with the insulatinginorganic film, damage to the organic semiconductor film, which could becaused by the formation of the microstructure body, can be reduced,whereby influence on electrical properties of the organic TFT can bereduced. The protective film 322 covers at least the organicsemiconductor film 304.

Note that the organic TFT applied to the present invention is notlimited to the above-described bottom contact organic TFT and may be atop contact organic TFT. A method of manufacturing the top contactorganic TFT is briefly described below with reference to FIGS. 9B-1 and9B-2.

First, a gate electrode layer 407 is formed over an insulating substrate401 using a material and a method which are similar to those in the caseof the bottom contact organic TFT, and a gate insulating film 406 isformed to cover the gate electrode layer 407. Note that a base film 402is formed over the insulating substrate 401.

Note that the gate electrode layer 407 forms not only the gate electrodeof the thin film transistor but also the lower electrode of themicrostructure body.

Next, a filler material layer 418, an upper electrode layer 419, and astructure layer 420 of the microstructure body are formed. The fillermaterial layer 418 may be formed using a material and a method which aresimilar to those of the filler material layer 102 in Embodiment Mode 1.The upper electrode layer 419 may be formed using a material and amethod which are similar to those of the gate electrode layer 407. Thestructure layer 420 may be formed using a material and a method whichare similar to those of the structure layer 104.

Next, the organic semiconductor film 404 is formed over the gateinsulating film 406. Note that pentacene is used as the material for theorganic semiconductor film of this embodiment mode as well. However, thematerial for the organic semiconductor is not limited to this materialbut may be an organic molecular crystal or an organic high molecularcompound. As the organic molecular crystal, specifically, there arepolycyclic aromatic compounds, conjugated double bond compounds,carotenes, and macrocycle compounds; complexes of these compounds;phthalocyanine; charge transfer complexes (CT complexes); and the like.For example, it is possible to use anthracene, tetracene, pentacene,hexathiophene (6T), tetracyanoquinodimethane (TCNQ), atetrathiafulvalene-tetracyanoquinodimethane (TTF/TCNQ) complex,diphenylpicrylhydrazyl (DDPH), a pigment, a protein, aperylenetetracarboxylic acid derivative such as PTCDA, anaphthalenetetracarboxylic acid derivative such as NTCDA, or the like.Further, as the organic high molecular compound, specifically, there arepi-conjugated polymers, phthalocyanine metal complexes, iodinecomplexes, and the like. In particular, it is preferable to use api-conjugated polymer including a conjugated double bond, such aspolyacetylene, polyaniline, polypyrrole, polythienylene, a polythiophenederivative, poly(3-alkylthiophene), a polyparaphenylene derivative, or apolyparaphenylenevinylene derivative.

Further, a method by which a film having uniform thickness can be formedmay be used for forming the organic semiconductor film 404.Specifically, an evaporation method, a spin coating method, a barcoating method, a solution casting method, a dip coating method, or thelike may be used. Here, pentacene that is an organic semiconductormaterial is formed for the organic semiconductor film 404 over the gateinsulating film 406 by a vacuum evaporation method. Preferably, theorganic semiconductor film 404 is selectively formed by forming througha mask, for example.

Note that as pretreatment for forming the organic semiconductor film,ultraviolet light irradiation treatment or plasma treatment may beperformed on a surface over which the organic semiconductor film is tobe formed. The plasma treatment or the like makes it possible to realizeremoval of organic substances on the surface over which the organicsemiconductor film is to be formed and an improvement in work function(to facilitate electron injection). Alternatively, a film for improvingadhesion to surface over which the organic semiconductor film is to beformed or improving an interface state, for example, a self-assembledmonolayer (SAM) film, an orientation film, or the like may be formed.

Note that here, although the organic semiconductor film 404 is formedafter the filler material layer 418 is formed, the filler material layer418 may be formed after the organic semiconductor film 404 is formed.After the gate electrode layer 407 is formed, the filler material layer418 may be formed before a source or drain electrode layer 416 isformed. However, in order to improve electrical properties of theorganic semiconductor film, the organic semiconductor film 404 ispreferably formed after the filler material layer 418 is formed. In thatcase, the above ultraviolet light irradiation treatment or plasmatreatment is preferably performed after the formation of the fillermaterial layer 418 and before the formation of the organic semiconductorfilm 404.

Then, the source or drain electrode layer 416 is formed. The source ordrain electrode layer 416 may be formed using a material and a methodwhich are similar to those in the case of the bottom contact organicTFT.

Note that an ohmic contact between the source or drain electrode layer416 and the organic semiconductor film 404 is needed. Therefore, when amaterial for the organic semiconductor film has p-type conductivity, amaterial having a work function higher than the ionization potential ofthe material of the organic semiconductor film is preferably used; whenthe material for the organic semiconductor film has n-type conductivity,a material having a work function lower than the ionization potential ofthe material of the organic semiconductor film is preferably used. Here,since pentacene that is a p-type material is used as the material forthe organic semiconductor film, tungsten having relatively a high workfunction is used as the material for the source or drain electrode layer416.

Then, after the organic semiconductor film is formed, the insulatingsubstrate 401 is subjected to heat treatment. The upper limit of thetemperature for the heat treatment is lower than the temperature atwhich the organic semiconductor film 404 is vaporized or decomposed.Heat treatment at a high temperature within this range improvescharacteristics of the organic TFT. Further, the temperature at thistime is preferably less than or equal to the melting point of theorganic semiconductor film.

Note that heat treatment may be performed in an atmosphere butpreferably in an inert gas atmosphere of nitrogen, argon, or the like inconsideration of deterioration of the organic semiconductor film due tooxygen or water. Furthermore, the heat treatment is more preferablyperformed in a reduced pressure (e.g., 1.3×10⁻³ to 6.7×10⁴ Pa).

Note that the present invention is not limited to the above description,and that the microstructure body may be formed after the organic TFT isformed or the organic TFT may be formed after the microstructure body isformed.

As described above, the bottom contact organic TFT and themicrostructure body can be formed over one substrate (see FIGS. 9B-1 and9B-2).

Note that the organic TFT of the present invention is preferably coveredwith a protective film. Here, an insulating inorganic film is used asthe protective film. By covering the organic TFT with the insulatinginorganic film, damage to the organic semiconductor film, which could becaused by the formation of the microstructure body, can be reduced,whereby influence on electrical properties of the organic TFT can bereduced. The protective film 422 covers at least the organicsemiconductor film 404.

Note that although the case is described above in which the lowerelectrode of the microstructure body and the gate electrode of themicrostructure body are formed by patterning one layer by one step andthe upper electrode of the microstructure body and the source or drainelectrode are formed by patterning one layer by one step, the presentinvention is not limited to this case. For example, even when theorganic TFT is used, it is not necessary that the lower electrode of themicrostructure body and the gate electrode of the microstructure bodyare formed by patterning one layer by one step and the upper electrodeof the microstructure body and the source or drain electrode are formedby patterning one layer by one step.

Further, according to the present invention, by forming themicrostructure and the semiconductor element over one substrate, asemiconductor device which does not need to be assembled or packaged anddoes not require high manufacturing cost can be provided. Further,manufacturing steps can be greatly reduced.

As described above, it is possible to form the microstructure body ofthe present invention and the transistor over one substrate. Further, asdescribed above, the microstructure body of the present invention can bemanufactured applying any of a variety of methods.

The microstructure body of the present invention, which is manufacturedas described above, can be applied to a pressure sensor or a displaydevice or the like using an interference method.

(Embodiment Mode 3)

By applying the present invention, a strain gauge can be manufactured.In this embodiment mode, a strain gauge to which the present inventionis applied is described with reference to drawings.

FIGS. 12A and 12B are schematic views showing the strain gaugemanufactured using the microstructure body to which the presentinvention is applied.

Note that FIG. 12B is a top view and FIG. 12A is a cross-sectional viewtaken along a line X-X′ in FIG. 12B.

In the microstructure body shown in FIGS. 12A and 12B, a filler materiallayer 501 is provided over a substrate 500, a conductive layer 502 isprovided over the filler material layer 501, and a structure layer 503is provided over the conductive layer 502. The conductive layer 502 ispatterned so as to have a predetermined length.

Here, the strain gauge is described. The term “strain gauge” means ameasuring device that can measure the amount of change in resistancevalue, which is generated when an object is strained, and can measurethe strain amount from this amount of change. This amount of change inresistance value is extremely small and therefore detected by beingconverted to voltage with the use of a Wheatstone bridge circuit.

FIG. 13 illustrates a Wheatstone bridge circuit used in this embodimentmode. The Wheatstone bridge circuit illustrated in FIG. 13 includes astrain gauge 510, a first resistor element 511, a second resistorelement 512, and a resistor element 513, which is a generally well-knownstructure in which one of four resistor elements included in aWheatstone bridge circuit is a strain gauge. When r denotes the initialresistance value of the strain gauge, R₁ denotes the resistance value ofthe first resistor element 511, R₂ denotes the resistance value of thesecond resistor element 512, and R₃ denotes the resistance value of thethird resistor element 513, output voltage V_(out) and input voltageV_(in) satisfy the following equation (4).

$\begin{matrix}{V_{out} = {\frac{{rR}_{2} - {R_{1}R_{3}}}{\left( {r + R_{1}} \right)\left( {R_{2} + R_{3}} \right)}V_{in}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

Here, in the case of r=R₁=R₂=R₃=R, when a strain is introduced to thestrain gauge to change the resistance value to R+ΔR, the amount ofchange ΔV_(out) in output voltage V_(out) is represented by thefollowing equation (5).

$\begin{matrix}{V_{out} = {\frac{\Delta\; R}{{4\; R} + {2\Delta\; R}}V_{in}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

When the resistance value R is sufficiently large, ΔR is much less thanR, and accordingly ΔV_(out) is represented by the following equation(6).

$\begin{matrix}{{\Delta\; V_{out}} = {{\frac{\Delta\; R}{{4\; R} + {2\Delta\; R}}V_{in}} = {\frac{V_{in}}{4}ɛ\; K}}} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

Here, K denotes an experimentally obtained gauge rate and is a constantvalue. The equation ∈K=ΔR/R is satisfied between the strain amount ∈ andthe gauge rate K. Therefore, by measuring ΔR, the strain amount ∈ can beobtained. The strain gauges described in this embodiment mode may bearranged in matrix.

Manufacture of the strain gauge by applying the microstructure body ofthe present invention makes it possible to prevent the structure layerfrom being damaged. Thus, a strain gauge having a movable portion withhigh mechanical strength and high reliability can be provided. Further,yield in the manufacturing process of the strain gauge can be improved.

This application is based on Japanese Patent Application serial no.2007-289224 filed with Japan Patent Office on Nov. 7, 2007, the entirecontents of which are hereby incorporated by reference.

1. A method of manufacturing a micro-electro-mechanical device,comprising: forming a lower electrode layer on an insulating surface;forming a first filler material layer including plural kinds ofmaterials over the lower electrode layer; inducing phase separation inthe first filler material layer; forming an upper electrode layer overthe first filler material layer; forming a structure layer over theupper electrode layer; and forming a porous second filler material layerby removing any of the materials included in the first filler materiallayer.
 2. The method according to claim 1, wherein any of the materialsincluded in the first filler material layer is removed by etching. 3.The method according to claim 1, wherein a porosity of the second fillermaterial layer is greater than or equal to 20% and less than or equal to80%.
 4. The method according to claim 1, wherein the structure layerincludes a portion capable of moving in a direction toward the lowerelectrode layer or in a direction opposite to the direction toward thelower electrode layer.
 5. The method according to claim 1, wherein theporous second filler material layer has a cylinder structure, a gyroidstructure, or a lamellar structure.
 6. The method according to claim 1,wherein the first filler material layer is formed so as to cover thelower electrode layer.
 7. A method of manufacturing amicro-electro-mechanical device, comprising: forming a lower electrodelayer on an insulating surface; covering an entire surface of the lowerelectrode layer with a film including block copolymer, the blockcopolymer including plural kinds of materials; selectively forming amask over the film including block copolymer; forming a first fillermaterial layer by etching the film including block copolymer using themask; forming an upper electrode layer over the first filler materiallayer; forming a structure layer over the upper electrode layer, andforming a porous second filler material layer by removing any of theplural kinds of materials included in the block copolymer.
 8. The methodaccording to claim 7, wherein the mask is a metal mask.
 9. The methodaccording to claim 7, wherein any of the materials included in the firstfiller material layer is removed by etching.
 10. The method according toclaim 7, wherein a porosity of the second filler material layer isgreater than or equal to 20% and less than or equal to 80%.
 11. Themethod according to claim 7, wherein the structure layer includes aportion capable of moving in a direction toward the lower electrodelayer or in a direction opposite to the direction toward the lowerelectrode layer.
 12. The method according to claim 7, wherein the blockcopolymer includes at least one material selected from a groupconsisting of hydrophobic aromatic hydrocarbon, hydrophobic aliphaticunsaturation hydrocarbon, hydrophilic aliphatic hydrocarbon, hydrophilicaromatic hydrocarbon, hydrophobic siloxane, and metal complex.
 13. Themethod according to claim 7, wherein the block copolymer includes atleast one material selected from a group consisting ofpolymethylmethacrylate, polystyrene, polyfluorene, polybutadiene,polyisoprene, polyvinyl alcohol, polyethylene glycol, polyvinylpyridine, polystyrene sulfonic acid, poly dimethylsiloxane, and polyferrocene.
 14. The method according to claim 7, wherein the poroussecond filler material layer has a cylinder structure, a gyroidstructure, or a lamellar structure.
 15. A method of manufacturing amicro-electro-mechanical device, comprising: forming a lower electrodelayer on an insulating surface; forming a first filler material layerincluding plural kinds of materials covering and in direct contact withthe lower electrode layer; forming an upper electrode layer over thefirst filler material layer; forming a structure layer over the upperelectrode layer; and forming a porous second filler material layer byremoving any of the materials included in the first filler materiallayer.
 16. The method according to claim 15, further comprising:inducing phase separation in the first filler material layer.
 17. Themethod according to claim 15, wherein the structure layer includes aportion capable of moving in a direction toward the lower electrodelayer or in a direction opposite to the direction toward the lowerelectrode layer.
 18. The method according to claim 15, wherein theporous second filler material layer has a cylinder structure, a gyroidstructure, or a lamellar structure.
 19. The method according to claim15, wherein the first filler material layer comprises a block copolymerincluding at least one material selected from a group consisting ofhydrophobic aromatic hydrocarbon, hydrophobic aliphatic unsaturationhydrocarbon, hydrophilic aliphatic hydrocarbon, hydrophilic aromatichydrocarbon, hydrophobic siloxane, and metal complex.
 20. The methodaccording to claim 15, wherein the first filler material layer comprisesa block copolymer including at least one material selected from a groupconsisting of polymethylmethacrylate, polystyrene, polyfluorene,polybutadiene, polyisoprene, polyvinyl alcohol, polyethylene glycol,polyvinyl pyridine, polystyrene sulfonic acid, poly dimethylsiloxane,and poly ferrocene.